void swap_v(int a, int b)
{
    int temp;
    temp = a;
    a = b;
    b = temp;
}

void swap_r(int &a, int &b)
{
    int temp;
    temp = a;
    a = b;
    b = temp;
}

void swap_cr(const int &a, const int &b)
{
    int temp;
    temp = a;
    a = b;
    b = temp;
}